1. Technical Field
The present invention relates to an image reading device which includes a flatbed-type document stand, and a document transport unit such as an automatic document feeder (ADF), and performs reading of a document which is fixed at the document stand, and reading of a document which is being transported at a reading position located in the middle of a transport path of the document transport unit using a reading unit included in a carriage which can move along the document which is fixed at the document stand.
2. Related Art
In the related art, as an image reading device, an apparatus which includes a flatbed-type document stand and an automatic document transport device (hereinafter, also referred to as Auto Document Feeder (ADF)) (as an example of document transport unit) was known. The image reading device includes a carriage which includes a reading unit such as a line sensor which reads a document on document stand glass from the lower part of the document stand, and a document stand cover which presses the document on the document stand. For example, an ADF is provided on the higher side (rear face side) of the document stand cover (for example, refer to JP-A-9-74465). In the image reading device of this type, an image of a document on the document stand is read using the reading unit by moving the carriage in the sub-scanning direction. In addition, documents which are in the middle of being transported from the ADF are sequentially read in the reading unit in a state in which the carriage is stopped at a reading position. In this manner, the image reading device which is disclosed in JP-A-9-74465 corresponds to a fixed document reading mode in which a document fixed at a document stand is read (corresponding to first mode), and a moving document reading mode in which a document which is being transported (being moved) from an automatic document transport device is read (corresponding to second mode).
In addition, in the image reading device of this type, a shading correction in which the entire image is corrected so as to have uniform brightness in average in order to reduce uneven density of the image is performed, and the apparatus includes a white reference plate which is read using a reading unit in order to obtain white reference data which is used when detecting density of a white level, or in the shading correction (refer to JP-A-9-74465). The carriage is moved to a reading position of the white reference plate, the reading unit reads reflected light of light with which the white reference plate is irradiated, and the white reference data is obtained, and is stored in a storage unit. In addition, image data of a document is generated by performing various corrections including the shading correction using the white reference data with respect to read data which is obtained by reading a document using the reading unit.
For example, in JP-A-9-74465, two white reference plates of a white reference plate which is provided in a document reading unit at a time of automatic document transport, and of a white reference plate which is used when reading a document which is in the outside of a document moving path, and is fixed at a document stand are included. In addition, a traveling body (carriage) reads the white reference plate for document stand which is located out of the document moving path before reading one document at a time of reading a plurality of documents which are transported from an automatic document transport device, and after reading the white reference plate, the carriage moves to a position of a document reading unit at the time of automatic document transport, and reads one document which is transported at the time of automatic document transport. In addition, when reading a second document and the following documents, the carriage reads a white reference plate in the document moving path which is located in the document reading unit. In the related art, since a white reference plate out of the document moving path is firstly read, it is possible to reduce an adverse effect which is applied at a time of detecting density of a white level due to attaching of dust, or the like, to the white reference plate, or at a time of a shading correction, when receiving a job of reading a plurality of documents.
Meanwhile, in JP-A-9-74465, the white reference plate for document stand which is located out of the document moving path is read before reading one document at a time of reading a plurality of documents which are transported from the automatic document transport device. For this reason, when a job of reading the plurality of documents is continued, it is necessary to move the traveling body to a position of the white reference plate for document stand which is located out of the document moving path from a position of the reading unit in the moving document reading mode. In addition, the traveling body moves to the reading unit of the document which is transported from the automatic document transport device after reading the white reference plate for document stand, and starts a reading operation of the document in the reading unit. For this reason, it takes for the traveling body a relatively long moving time in order to read the white reference plate, and as a result, there is a problem in that a starting period of a reading operation of a document is delayed.